1. Field of the Invention
The invention relates to a motor vehicle door lock with an electromechanical central locking system drive.
2. Description of Related Art
A conventional motor vehicle door lock of the type under consideration, therefore the lock for a motor vehicle side door, a rear hatch or a rear door, but also for a sliding door of a motor vehicle, generally has locking elements, such as a latch and ratchet, and a lock mechanism with various levers which are used for actuation. In particular, reference can be made to the prior art (for example, published German Patent Application DE 100 06 765 A1 and corresponding U.S. Pat. No. 5,673,578).
Motor vehicle door locks with an electromechanical central locking system drive (for example, German Patent Application DE 100 06 765 A1 and corresponding U.S. Pat. No. 5,673,578) are common. It generally drives a mechanical central locking system element of the lock mechanism in order to move the motor vehicle door lock, overall, at least into a unlocked position, in which the motor vehicle door can be opened from the inside and outside, and into a locked position in which the motor vehicle door can be opened from the inside, but cannot be opened from the outside. Often, a third position is also set up, specifically an antitheft position, in which the motor vehicle door cannot be opened either from the outside or from the inside. Finally, on the rear side doors and on the rear doors, there can also be a child safety position in which the motor vehicle door can be opened from the outside, but not from the inside. The details in this respect are not important to the teaching of this invention, which relates to the control of the electromechanical central locking system drive.
The known motor vehicle door lock underlying the invention (German Patent Application DE 33 39 479 A1 and corresponding U.S. Pat. No. 5,673,578), first of all, has an electromechanical central locking system drive and a mechanical central locking system element driven by it, in the form of a central locking system drive lever. In this prior art, the central locking system drive encompasses an electric drive motor, a linkage with a gearwheel which forms the driven element, and driver journal which is located on the gearwheel and via which the central locking system element which is made as a pivot lever can be pivoted back and forth between two positions, the unlocked position and the locked position. The construction here is such that the central locking system element with the electric drive motor switched off is decoupled from the drive motor and can be mechanically moved free of resistance from one position into another, for example by actuating a closing cylinder.
This motor vehicle door lock has an electronic motor control. The latter encompasses a motor state sensor in the form of a motor current sensor which measures the current drawn by the electric drive motor. The motor control is designed such that it directly triggers or automatically triggers the electric drive motor for driving the central locking system element into the locking position either after receiving an actuation signal from an actuation unit such as a closing cylinder, a locking button, a remote control receiving unit or a handle (inside door handle, outside door handle), as soon as a certain operating state of the motor vehicle has been reached. The latter, of course, requires an actuation signal, which is not initiated by an operator, but it is automatically initiated when a certain operating state of the motor vehicle is reached. Such an operating state is, for example, a certain minimum speed of the motor vehicle after being parked beforehand. This function of the known motor vehicle door lock is used to protect passengers against hold-ups at traffic lights or the like. When the operator has climbed into the vehicle, has started the engine and has set off, all door locks of the motor vehicle are automatically locked when a minimum speed of the motor vehicle is exceeded and they remain locked until the operator climbs out again.
In the known motor vehicle door lock explained above, the motor control can do something else, for example it can turn off the electric drive motor when the locked position (or the unlocked position) is reached. Here it is provided specifically that to turn off the electric drive motor there is at least one stop which blocks further rotation of the electric drive motor. The motor control is designed such that the electric drive motor is turned off at least when the locked position is reached according to the signal of the motor state sensor. In the motor current sensor which is known in the prior art, this means that the power consumption of the electric drive motor is monitored and the electric drive motor is turned off when a certain boundary value of the motor current is exceeded beyond a certain time. This is evaluated in the motor control as blocking of the motor by the central locking system element or the stop, then the electric drive motor is turned off. This is called blocking operation of the electric drive motor. This makes it possible to abandon microswitches which sense certain positions of the electric drive motor of the step-down gearing, generally downstream of it and/or of the mechanical central locking system element. This saves money and reduces fault susceptibility of the motor vehicle door lock.
In practice, it has been shown that in motor vehicle door locks with electromechanical central locking system drives with automatic locking as a result of reaching a defined operating state of the motor vehicle, the noise of the central locking system drive when being turned off is perceived as disturbing. This applies when the turning-off takes place by means of microswitches because the lock mechanism is also stopped suddenly in this case. This applies to a special degree in blocking operation of the electric drive motor because a mechanical element strikes a stop in some form and is thus stopped.
Very similar disturbing noise occurs when the electric drive motor, after receiving an actuation signal from the actuation unit, is to a certain extent deliberately stopped by the operator. However, in this case, this noise is perceived as less disturbing because the operator is more or less prepared for it.